This invention relates to a yoke type magnetoresistive head.
In a magnetic recording device such as a hard disk drive (HDD), a super high density recording of as high as 10 GB (gigabits) per square inch is now aimed at as the next target. For improvement of recording density of a recording medium, it is required to improve track density by making recording track width narrow and, at the same time, to improve linear density in the recording track direction. For read-out from a recording medium of narrow track width, a reproducing head of high sensitivity is required. In order to meet this requirement, use of a magnetic head utilizing a giant magnetoresistive effect, which can generate an extremely large rate of resistance change is more preferable rather than the conventional magnetic head utilizing an anisotropic magnetoresistance effect. Further, for read-out from a recording medium of high linear density, it is important to reduce head-medium spacing so as to realize an in-contact operation or a pseudo-contact operation, and also important to reduce reproducing gap length.
A shielded MR head is conventionally known. The shielded MR head is constructed such that a magnetoresistive element (MR element) is disposed near the air-bearing surface (ABS) of a head substrate which faces the recording medium, and magnetic shields are disposed to the both sides of the MR element. However, since a sense current is allowed to flow through the MR element, if the MR element is brought into contact with a recording medium, the MR element is electrically unstabilized and may be electrically broken down in the worst case. In addition, due to heat generated by contact with the recording medium, the temperature of the MR element may be raised, resulting in unstable head operation. Further, in the structure that the MR element is interposed between the magnetic shields, it is difficult to reduce gap length.
With a view to overcome the aforementioned problems, a yoke type MR head has been proposed (for example, IEEE Trans. Magn., Vol. MAG-26(1990)2406). This yoke type MR head comprises a magnetic yoke which is formed on a head substrate so as to define magnetic gap at the air-bearing surface, and a couple of MR elements which are electrically insulated from the magnetic yoke. The MR elements are designed to allow a sense current to pass along the film surface. Since the magnetic yoke is electrically insulated from the MR elements in this structure, even if the magnetic yoke is brought into contact with the recording medium, the MR elements would not be badly affected. Since the MR elements and electrodes need not to be disposed in the magnetic gap defined by the magnetic yoke, the gap length can be easily reduced.
On the other hand, since the reproducing sensitivity is greatly deteriorated if the MR elements are disposed remote from the air-bearing surface in this MR head, the MR elements are required to be disposed as close to ABS as possible in order to obtain a sufficient reproducing sensitivity. However, if a GMR element made of stacked metal films such as a spin valve is disposed close to a recording medium, it becomes difficult to ensure electric insulation against the magnetic yoke or to form electrodes.